Line_Horizon — draws a one-sided line as if it were an infinite distance away.
Line_Horizon ();
Line_Horizon does not take any parameters.
Line_Horizon cannot be used from inside a script. It must be placed on a line. However, you can use SetLineSpecial to place Line_Horizon on a line or remove it as desired while the level is played.
When you place the Line_Horizon special on a line, that line will not be drawn. Instead, the floor and ceiling in front of that line will be extended to infinity until they meet at the horizon (hence the name). This special should only be used on one-sided lines.
Line_Horizon is intended to be used with skyboxes so you can have a sky without a visible boundary. Without this special, you would have to resort to either making the skybox very large or hiding the edge of the sky behind some sufficiently tall foreground graphics such as mountains.
Line_Horizon does not work with sloped floors or ceilings. If you try to use it with them, the result will look weird and not at all right.
ZDoom 1.23 beta 29